Field of the Invention
The present disclosure relates to an image forming system which comprises an image forming apparatus such as an electrophotographic printer and various accessory devices connected to the image forming apparatus.
Description of the Related Art
An image forming system is configured by an image forming apparatus and an accessory device. In the system, the accessory device, such as a sheet feeding device, a stacker, a book binding device, a finisher and the like, are connected to the image forming apparatus. The image forming apparatus and the accessory device of the image forming system are connected through a bus topology network to establish data communication therebetween. By freely constituting each device, high-speed communication can be established through the bus topology network.
In the image forming system, the image forming apparatus and the accessory device are connected in series. Sheet delivery is performed between the devices. Thus, each device is required to at least identify adjacent device and transmit/receive information required for sheet delivery to/from the device. To identify each device in the image forming system, identification information, which is unique to a device and is called node ID, is assigned to each device. It is generally known that, in bus topology, device is identified by the node ID to establish communication between devices. Each device connected to the bus topology network is capable of recognizing the type of device connected by the node ID. However, it is difficult to physically recognize an order in which each device is connected unless performing some methods for identifying the connected device each time the device is connected, etc.
In case of the image forming system, it is general that the node ID is managed by the image forming apparatus. The image forming apparatus holds a connection order of the accessory devices in the built-in memory. Then, the image forming apparatus compares the detection result obtained by the detection of the connection state by performing the method for identifying etc., with the connection order held in the memory. Through this, the image forming apparatus confirms the connection state. If the connection order held in the memory does not match the detection result, the image forming apparatus notifies a user that an abnormality has occurred in the connection of the accessory devices and prompts the user to take some appropriate actions to solve the situation.
For example, in US2007/0086045(A1), when the connection order held does not match the detection result, the image forming apparatus displays a message. In the message, the user is prompted to input an instruction to disconnect the accessory device to make the apparatus available.
As a communication system, the US2007/0086045(A1) adapts ARCNET (Attached Resource Computer NETwork) to detect disconnection of the device from the network. However, in the US2007/0086045(A1), unless network reconfiguration processing is performed, it is not possible to determine the device which is disconnected from the network. Thus, it is difficult for the image forming apparatus to recognize the network configuration in real time.